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I have not used coir, but a friend experimented with it for seed starting this past spring. It was one of those domed kits, I forget which brand. She was less than enthused about the results. She also bought a different kit that featured a peat-based mixture, and that one did a lot better.

There was a post about this last spring with an article that basically said coir was not as effective as spagnum moss, but of course, I can't find it now. Also, coir is much more expensive, at least around here.

I'd go so far as to say it's non-renewable ...... because once you've used it once, you'll never use it again ...and then it can't be renewed if you don't use it in the first place ...LOL

In all seriousness ...

Pro's: great moisture indicator when used as a top mulch, doesn't change pH when used as an additive in potting mixture

Con's: Doesn't stay put, hard to mix, floats worse than perlite & vermiculite when wet, when wet, adheres to everything ...especially vegetation, goes airborne in the slightest breeze (don't work with this stuff on a hot, dry day if you wear contacts), unless completely saturated with water, rivulettes/ravines/trenches with even the most gentle application of water.

I've used coir for about a year now in my potting and seed starting mixes. It does fine, but it is a little more work to use. Most brands that I can afford needs to be washed before use. From what I understand when it is processed it is washed with sea or salt water so when you get it you need to wash it to get out the salt. Personally I go back and forth all the time.